1. Field of the Invention
The present invention relates to circuit boards, and more particularly, to a circuit board having a power source.
2. Description of the Prior Art
Power systems with compact size, light weight and high energy density are in great demand, for use in electronic/communication/3C products that are wireless and portable and have high-performance components having miniaturized profiles. Accordingly, more and more efforts are put in developing new energy solutions having smaller size, higher energy density, better safety and greater environment-friendliness. One of such energy solutions is so-called miniaturized “fuel cell”.
Fuel cells serve as a power generating device, and unlike rechargeable cells or disposable non-rechargeable cells, fuel cells must be fueled to maintain the power provided thereby, as the name suggests. Hydrogen is the fuel for fuel cells, such that fuel cells are considered as the “new energy” power system. As fuel cells have desirable properties of low pollution and efficient energy conversion, they have become a new generation power supply technology. A fuel cell works by reversing the process of electrolyzing water into oxygen and hydrogen, that is, electricity and water are produced. In other words, the fuel cell generates electricity by combining oxygen and hydrogen to form water. There are five types of fuel cells as follows:                (1) Alkaline Fuel Cell (AFC), using potassium hydroxide as electrolyte;        (2) Phosphoric Acid Fuel Cell (PAFC), using phosphoric acid (H3PO4) solution as electrolyte;        (3) Molten Carbonate Fuel Cell (MCFC), using molten carbonate as electrolyte;        (4) Solid Oxide Fuel Cell (SOFC), using zirconium dioxide as electrolyte; and        (5) Proton Exchange Membrane Fuel Cell (PEMFC), comprising Direct Methanol Fuel Cell (DMFC), directly using methanol as fuel, without in advance forming hydrogen gas.        
Despite their variety, all the fuel cells substantially have an anode, a cathode, and solid or liquid electrolyte between the anode and the cathode.
FIG. 1 schematically shows a full cell (an alkaline fuel cell 1 is exemplified) to illustrate the principle of power generation thereof. The alkaline fuel cell 1 uses potassium hydroxide (KOH) 11 as electrolyte. Hydrogen gas 12 enters the fuel cell 1 via an anode 13, and oxygen gas 14 (or air) enters the fuel cell 1 via a cathode 15. Reactants at the anode 13 and the cathode 15, driven by oxidation-reduction potential and in the presence of a catalyst, undergo the following reactions:anode half-reaction: 2H2+4OH−→4H2O+4e−cathode half-reaction: O2+2H2O+4e−→4OH−full reaction: 2H2+O2→2H2O.
The hydrogen gas 12 in contact with the anode 13 and OH− ions released by dissociation of the potassium hydroxide (KOH) 11 undergo an oxidation half-reaction, so as to produce water 16 and release electrons that are absorbed by the anode 13. Concurrently, the cathode 15 releases electrons, and the electrons, the oxygen gas 14 in contact with the cathode 15 and water 16 undergo a reduction half-reaction to produce OH− ions. As a result, a stream of electrons from the anode 13 through an external circuit 17 to the anode 15 is generated. According to the full reaction, water 16 is the only product discharged by the fuel cell 1. By the chemical reaction of hydrogen and oxygen to produce electricity and water, the fuel cell 1 causes no pollution and eliminates the need of time-consuming recharging required by conventional rechargeable cells, thereby representing a prominent new power source.
For the mainstream electronic products nowadays, semiconductor packages and power source components are separately fabricated, and then they are electrically interconnected and assembled. Normally, a fuel cell is disposed within a metal frame, and usually occupies a considerable space, thereby not favorable for miniaturization of the electronic products. And, there is usually a relatively long path of electrical connection between the semiconductor packages and the power source components, thereby undesirably increasing power consumption.
Accordingly, miniaturized fuel cells have become the focus of cell development in the industry. Referring to FIG. 2, which schematically shows a miniaturized fuel cell 2, the fuel cell 2 comprises: an electronically functional silicon substrate 20; a first metal layer 21 formed on the silicon substrate 20 and serving as an anode; an insulating frame member 22 disposed on the first metal layer 21, for receiving electrolyte 23 therein; and a porous second metal layer 24 formed on the insulating frame member 22 and serving as a cathode. Both the first metal layer 21 (the anode) and the second metal layer 24 (the cathode) are in contact with the electrolyte 23 inside the insulating frame member 22 so as to form a path for providing power to the silicon substrate 20.
However, the silicon substrate 20 of the fuel cell 2 is fragile and is not cost-effective to fabricate, and its raw materials are not reliably available. And, the electrolyte 23 carried by the silicon substrate 20 is susceptible to leakage. As such, the fuel cell 2 is not meeting the need for miniaturization.
Therefore, the problem to be solved here is to improve existing fuel cells so as to achieve multi-module system integration for the sake of miniaturization and versatility thereof.